Patients with congestive heart failure, who are being treated with digitalis, exhibit beta-adrenoreceptor desensitization in lymphocytes. The relationship between desensitization and the duration of changes in plasma norepinephrine, dopamine beta-hydroxylase is being studied. The contribution of digitalis to this process will also be evaluated. Alterations in alpha and beta adrenoreceptor numbers and affinity will be studied using labeled ligands.